LUTHER BURBANK 



a white guinea pig with a rough coat. Now we 

 have already seen that blackness is dominant to 

 whiteness as regards the coat of the guinea pig, 

 and we must further understand that roughness 

 of coat is known to be dominant to smoothness. 



We must expect, then (according to Professor 

 Castle) , that when a cross is made, the guinea pigs 

 of the first filial generation will, unlike either 

 parent, be black in color and rough as to coat. 



But, in the succeeding generation, the black, 

 rough-coated guinea pigs being interbred, there 

 will be a certain number of offspring that combine 

 the dominant characters of blackness and rough- 

 ness of coat, and will breed true to these; a certain 

 number will be black and rough-coated, but will 

 bear the latent characters of smoothness and 

 whiteness of coat which will reappear in their 

 progeny; and, finally, there will appear individ- 

 uals combining the two recessive traits of white- 

 ness and smoothness of coat. 



These white, smooth-coated individuals are 

 obviously different from their parents, and 

 different also from either of their grandparents. 

 They constitute a new race, sprung into being in 

 a single generation, and a race that will necessarily 

 breed true as to the character of smooth coat and 

 white coat, because they are "homozygous" as to 

 the factors for both these recessive characters. 



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